Fuel cell integrated humidification

Abstract

A device and method to extract water from a moisture-rich fuel cell flowpath to supply other components of a fuel cell system that require water. A water transport unit is integrated into the fuel cell so that the size, weight and complexity of a fuel cell is minimized. In one embodiment, the device includes numerous flowpaths that include an active region and an inactive region. The water transport unit includes a moisture-donating fluid channel and a moisture-accepting fluid channel, where the latter is fluidly connected with a portion of the fuel cell that is in need of humidification. Upon passage of a moisture-donating fluid through the inactive region of the device flowpath, at least some of the water contained therein passes through the water transport unit to a portion of the fuel cell that is in need of humidification.

1. A fuel cell assembly comprising:
 a plurality of fuel cells arranged as a stack, each of said fuel cells comprising:
 an anode configured to accept a hydrogen-bearing reactant; 
 a cathode configured to accept an oxygen-bearing reactant; and 
 a bipolar plate disposed between said anode and said cathode such that an anode flowpath and a cathode flowpath defined on opposing surfaces of said bipolar plate are configured such that a respective one of said hydrogen-bearing reactant and said oxygen-bearing reactant may be delivered to a corresponding one of said anode and said cathode, said anode flowpath and said cathode flowpath arranged such that at least a portion of a travel distance therealong defines:
 an active region formed along a portion of a surface of said bipolar plate, said active region adjacent a respective one of said anode and said cathode to facilitate a catalytic reaction therebetween, and 
 an inactive region formed along a portion of said surface of said bipolar plate that is spaced away from said active region, said inactive region configured such that a catalytic reaction does not take place therein; and 
 
 
 a water transport unit placed between an adjacently stacked anode and cathode within at least said inactive region such that they are in moisture exchange communication with one another, said water transport unit comprising:
 a moisture-donating fluid channel configured to receive flow from at least one moisture-rich flowpath in said bipolar plate that corresponds to one of said adjacently stacked anode or cathode; and 
 a moisture-accepting fluid channel configured to deliver flow to the other of said flowpath in said bipolar plate that corresponds to said anode or said cathode, said moisture-accepting fluid channel cooperative with said moisture-donating fluid channel such that upon passage of a moisture-donating fluid through the latter, at least some of the water contained therein passes to the former, wherein said moisture-donating fluid channel and said moisture-accepting fluid channel are separated by a moisture-permeable membrane, and wherein at least one side of said moisture-permeable membrane is substantially covered with a hydrophilic diffusion media. 
 
 
     
     
       2. The assembly of  claim 1 , wherein said active region defines a substantial center of said at least one fuel cell. 
     
     
       3. The assembly of  claim 1 , further comprising a plurality of flow headers, each of which are disposed at opposing ends of said plurality of flowpaths and define manifolds therefor. 
     
     
       4. The assembly of  claim 1 , further comprising at least one coolant flowpath placed in thermal communication with at least one of said anode and said cathode. 
     
     
       5. The assembly of  claim 1 , wherein said moisture-donating fluid channel and said moisture-accepting fluid channel are arranged in substantial counterflow relationship with one another. 
     
     
       6. The assembly of  claim 1 , wherein said moisture-donating fluid channel is fluidly coupled to said portion of flowpaths that are in fluid communication with said cathode such that an exhaust fluid produced by said electrochemical reaction can flow through said moisture-donating fluid channel in order to give up at least a portion of the water contained in said exhaust fluid to said moisture-accepting fluid channel. 
     
     
       7. The assembly of  claim 6 , wherein said moisture-accepting fluid channel is fluidly coupled to said portion of flowpaths that are in fluid communication with said anode such that upon receipt of said portion of the water from said moisture-donating fluid channel, said portion of flowpaths that are in fluid communication with said anode can convey said hydrogen-bearing fluid and said portion of the water to said anode. 
     
     
       8. The assembly of  claim 6 , wherein said moisture-rich flowpath is a cathode exhaust, and said portion of said fuel cell that is in need of humidification is an anode inlet. 
     
     
       9. The assembly of  claim 6 , wherein said moisture-rich flowpath is a cathode exhaust, and said portion of said fuel cell that is in need of humidification is a membrane that is disposed between said anode and said cathode flow channels. 
     
     
       10. The assembly of  claim 6 , further comprising an anode recirculation loop fluidly coupled to said anode. 
     
     
       11. The assembly of  claim 1 , wherein said moisture-donating fluid channel is common with said at least one moisture-rich flowpath. 
     
     
       12. A vehicle comprising the fuel cell assembly of  claim 1 , wherein said fuel cell assembly serves as a source of motive power for a vehicle.